The present invention relates generally to a projection optical apparatus, and more particularly to a projection optical apparatus incorporating a diffusing plate comprising a hologram.
So far, various projection optical apparatuses with diffusing holograms incorporated therein as screens have been proposed in the art. However, a screen incorporating a conventional diffusion hologram is used to diffuse light coming from an image projected onto a screen plane in such a way that the light is spread over to some extents. This is also true for an ordinary diffusing screen with white pigments or transparent particles contained in it. However, the diffusion hologram, because of being capable of limiting the angle of diffusion of diffuse light leaving the same, can project a relatively bright image.